Safety mechanism for stopping a machine



June 13, 1967 w. GOURLEY ETAL 3,325,611

SAFETY MECHANISM FOR STOPPING A MACHINE Filed March 8, 1966 POWER SOURCE T0 N0 TOR CONTROL //VVENTO/?S WILLIAM L. GOURLEY and CHARLES A. JAN/{ER 4 Mom ay United States Patent 3,325,611 SAFETY MECHANISM FoR STOPPING 4 Claims. (Cl. 200-6139) This invention relates to an improved safety mechanism for stopping a machine when trouble is imminent.

Although our invention is not thus limited, one application for which we have found the mechanism particularly useful is in a slabbing mill for rolling steel ingots. A conventional slabbing mill includes spindles which are connected to respective drive shafts through universal or crab couplings. In the event any of these parts break, substantial damage can occur unless the mill is stopped promptly. As we explain hereinafter, our mechanism not only stops a rolling mill or other machine when actual breakage occurs, but when there is excessive vibration or even a nearby fire.

An object of our invention is to provide an improved safety mechanism which automatically stops a machine in the face of imminent trouble, and prevents the machine from starting until reset intentionally.

A further object is to provide an improved safety mechanism of the foregoing type which includes a cable or the like surrounding a rotating element and arranged to stop the machines whenever it is disturbed, that is, electrically grounded, pulled, broken or slackened.

A further object is to provide a safety device of the foregoing type which we can apply readily to existing machines with only minor alterations to their structure.

In the drawing:

FIGURE 1 is a side elevational view with parts broken away of a portion of a slabbing mill equipped with our safety mechanism;

FIGURE 2 is a vertical section II-II of FIGURE 1;

FIGURE 3 is a sectional view on a still larger scale on line III-III of FIGURE 2; and

FIGURE 4 is a schematic wiring diagram.

FIGURES 1 and 2. show a portion of a conventional slabbing mill as a typical machine to which we can apply our safety mechanism. The portion of the mill shown includes a pair of drive motors 10, drive shafts 12, spindles 13, and universal couplings 14 connecting the drive shafts to the spindles. The spindles lead to the mill rolls for driving them, yet allowing for necessary adjustments. A frame 15 opposite the universal couplings forms a convenient mounting for our safety mechanisms. Preferably we include separate safety mechanisms for each spindle, but since the two are alike, we describe only the lower one.

Our safety mechanish comprises a metal ring 18 which encircle spindle 13 at the universal coupling 14. Conveniently we support ring 18 on upper and lower bars 19 and 20 which extend across frame 15 above and below the spindle. We attach a plurality of blocks 21 of insulating material to ring 18 spaced around its inside circumference. As best shown in FIGURE 3, each block carries a respective stub shaft 22 on which we mount a roller 23 of insulating material. We string an electrically conductive cable 24 around the rollers 23 encircling spindle 13 but normally out of contact therewith. In the example of a slabbing mill, the cable lies in the plane of the spade portion of the coupling. We anchor one end of the cable to the shaft of one of the rollers 23a, and we extend a portion 24a of the cable sideways from an adjacent roller 23]). We attach the extending portion 24a of the cable to on a larger scale on line one end of a tension spring 25. We attach the other end of the spring to an insulated bracket 26 mounted on frame 15. We mount an electric control box 27 on frame 15 above the cable. The box has a downwardly extending operating lever 28, which we attach to the cable. When the parts are properly adjusted, spring 25 maintains sufii cient tension in cable 24 to hold the operating level 28 in a mid-position.

As shown in FIGURE 4, the circuit within the control box 27 includes a pair of adjacent windings 31 and 32. We connect one winding 31 to an AC source 33. As long as the other winding 32 is in an open circuit, no current flows therethrough. If opposite ends of the winding 32 are connected together to form a closed loop, A-C flowing through winding 31 induces current flow through winding 32. The latter winding has an armature which controls a normally closed contact 32a and a normally open contact 32b. The normally closed contact 32a is in a circuit 34 which controls the drive motors 10. We connect the normally open contact 32b in series with a reset button 35 between opposite ends of winding 32. Whenever current is induced in winding 32, contact 32a opens and stops both drive motors 10. Contact 32b closes to seal in the loop through the winding. This loop can be opened only if the reset button 35 is actuated. Consequently the drive motors do not start inadvertently.

The circuit illustrated completes the loop through the winding 32 whenever cable 24 is electrically grounded, pulled, broken or slackened. We connect one end of the winding 32 to the cable through a conductor 36 and the other end of the winding to a ground 37, whereby grounding the cable completes the loop. We connect parallel, normally open first and second microswitches 38 and 39 across the ends of the winding 32. We place these switches on opposite sides of the operating lever 28, whereby the lever closes one or the other of the switches to complete the loop whenever it moves significantly from its midposition. A pull on cable 24 moves lever 28 to the right against the action of spring 25 and thus closes switch 38. If cable 24 breaks or slackens, tension in spring 25 moves the lever to the left and closes switch 39. Preferably we mount both switches 38 and 39 so that we can adjust their positions and thereby adjust the sensitivity of the mechal'llSIl'l.

If the spindle 13 or universal coupling 14 breaks, one of the parts immediately strikes cable 24. Either the resulting electrical contact or mechanical pull acts to stop the drive motors. If the cable breaks, tension in spring 25 acts to stop the motors. Undue vibration of the spindle or other parts may cause one of the switches 38 or 39 to close "by mechanical action, or the spindle to make electric contact with the cable. If a fire heats the cable, the cable expands thermally and thus slackens. Therefore our safety mechanism effectively stops the machine whenever trouble is imminent before any serious damage occurs.

While we have shown and described only a single embodiment of our invention, it is apparent that modifications may arise. Therefore, we do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

We claim:

1. In a machine which includes a drive motor, means for energizing said motor, and a rotating element operatively connected with said motor, the combination therewith of a safety mechanism comprising an exposed electrically conductive flexible cable, means supporting said cable in a position in which the cable encircles said element but normally is out of contact therewith, a normally open electric circuit connected to said energizing means and in which said cable is connected electrically, and switch means mechanically connecting said cable with said circuit, said circuit being completed through said cable when contacted by said element to stop said motor, said circuit also being completed through said switch means when said cable is disturbed mechanically likewise to stop said motor.

2. In a machine which includes a drive motor and a rotating element operatively connected with said motor, the combination therewith of a safety mechanism comprising a supporting ring encircling said element, a plurality of insulators mounted on said ring and spaced around the circumference thereof, an electrically conductive cable strung around said insulators and being normally out of contact with said element, and an electric circuit operatively connected with said motor and said cable for stopping said motor when said cable is disturbed.

3. A combination as defined in claim 2 in which said circuit includes a winding, a contact connected with said drive motor and controlled by said Winding, electric switches connected to said winding, means connected to said cable for closing one of said switches when said cable is pulled, broken or slackened, one end of said winding being grounded and the other end being connected to-said cable, and means for energizing said winding and thereby operating said contact when one of said switches closes or said cable is grounded.

4. A combination as defined in claim 2 in which one end of said cable is anchored to one of said insulators and said cable has a portion extending sideways from one of said insulators, said mechanism further comprising a tension spring attached to the extending portion of said cable and a fixed frame to which a spring is attached, and in which said circuit is connected with the extending portion of said cable to be actuated when said cable is electrically grounded, pulled, broken or slackened.

References Cited UNITED STATES PATENTS 3,108,264 10/1963 Heinoo 200-6l.4 X

BERNARD A. GILHEANY, Primary Examiner. I. J. BAKER, H. GILSON, AssistantExaminers. 

1. IN A MACHINE WHICH INCLUDES A DRIVE MOTOR, MEANS FOR ENERGIZING SAID MOTOR, AND A ROTATING ELEMENT OPERATIVELY CONNECTED WITH SAID MOTOR, THE COMBINATION THEREWITH OF A SAFETY MECHANISM COMPRISING AN EXPOSED ELECTRICALLY CONDUCTIVE FLEXIBLE CABLE, MEANS SUPPORTING SAID CABLE IN A POSITION IN WHICH THE CABLE ENCIRCLES SAID ELEMENT BUT NORMALLY IS OUT OF CONTACT THEREWITH, A NORMALLY OPEN ELECTRIC CIRCUIT CONNECTED TO SAID ENERGIZING MEANS AND IN WHICH SAID CABLE IS CONNECTED ELECTRICALLY, SAID SWITCH MEANS MECHANICALLY CONNECTING SAID CABLE WITH SAID CIRCUIT, SAID CIRCUIT BEING COMPLETED THROUGH SAID CABLE WHEN CONTACTED BY SAID ELEMENT TO STOP SAID MOTOR, SAID CIRCUIT ALSO BEING COMPLETED THROUGH SAID SWITCH MEANS WHEN SAID CABLE IS DISTURBED MECHANICALLY LIKEWISE TO STOP SAID MOTOR. 